The present invention relates to antiperspirant stick compositions that contain relatively high suspending agent concentrations, but that still provide low residue performance and high antiperspirant efficacy.
There are many types of solid antiperspirant sticks that are commercially available or otherwise known in the antiperspirant art. These products typically contain an astringent material, e.g. zirconium or aluminum salts or combinations thereof, solubilized or dispersed in a suitable liquid carrier, and the solution or dispersion contained within a solid matrix that gives the product a solid stick form.
These solid antiperspirant sticks are ideally designed to provide effective perspiration and odor control while also being cosmetically acceptable during and after application onto the underarm area of the skin. In this context, cosmetically acceptable means that the product glides on smoothly during application, is non irritating, and results in little or no visible residue (e.g., low residue performance) after application to the skin.
Examples of solid antiperspirant sticks that provide good antiperspirant efficacy and low residue performance are described in U.S. Pat. No. 5,840,286 (Gardlik et al.) and U.S. Pat. No. 5,429,816 (Hofrichter et al.). Both disclose a variety of low residue antiperspirant sticks which contain an antiperspirant active, a suitable liquid carrier, and up to about 15% by weight of a low residue gellant such as 12-hydroxystearic acid or similar other materials.
Although low-residue solid antiperspirants with good antiperspirant efficacy such as those described by Gardlik et al. and Hofrichter et al. are now well known, these low-residue solids typically contain no more than about 15% by weight of a solid suspending agent. For some types of solid suspending agents, however, higher concentrations are needed in order to formulate a solid stick having the desired hardness and application rheology. Examples of such other suspending agents include a variety of solid triglycerides and other wax-like materials that generally require more than about 15% by weight. At these higher solid suspending agent concentrations, especially when formulated as a low-residue product, it becomes increasingly more difficult to maintain antiperspirant efficacy. It is known that many solid suspending agents at higher concentrations can inhibit release of antiperspirant active after application, and thus inhibit antiperspirant efficacy which is tied closely to antiperspirant release characteristics from the applied product matrix.
It has now been found that a low-residue antiperspirant stick can be formulated at solid suspending agent concentrations above 15% by weight of the composition, and still provide good antiperspirant efficacy. It has been found that by formulating the solid stick to provide low residue performance with a combination of volatile and nonvolatile silicones, solid antiperspirant active, and solid suspending agents, wherein the solid stick is preferably substantially free of any organic nonvolatile liquid having a C log P value greater than about 5.5, that a low residue, high-suspending agent concentration, solid stick can be formulated that also provides excellent antiperspirant efficacy. It has been found that the solid antiperspirant active is more effective when delivered from an anhydrous base containing a volatile and nonvolatile solvent that is also substantially free of relatively high C log P organic nonvolatile liquids. It is believed that this formulation allows for better release of antiperspirant active after application to the skin, and thus delivers improved antiperspirant efficacy even in the presence of relatively high solid suspending agent concentrations.
It is therefore an object of the present invention to provide a solid, low-residue, anhydrous antiperspirant stick that contains relatively high solid suspending agent concentrations but that still delivers improved antiperspirant efficacy.
The present invention is directed to anhydrous antiperspirant sticks comprising from about 0.5% to about 60% by weight of a particulate antiperspirant active; from about 16% to about 50% by weight of a solid suspending agent; from about 10% to about 80% by weight of a volatile silicone; and from about 1% to about 35% by weight of a non volatile silicone. The sticks are preferably substantially free of those nonvolatile organic liquids having a C log P value greater than 5.5. The sticks have a product hardness of at least about 600 gramxc2x7force and can be characterized in terms of low residue and/or high antiperspirant efficacy measures.
It has been found that, although these compositions can be formulated to contain relatively high concentrations of a solid suspending agent, they still provide improved low residue performance and high antiperspirant efficacy.